Plumbing vent (Stack) leak

I live in a home from the 1970s that has a mansard roof. (Flat roof, not attic access, in fact the space is only 12 inches high)

We have had roof repair people come to seal the perimter of the flat roof, replace the scupper (water drain) and to install new plumbing boots around the plumbing vent pipes. All of this was sealed properly. During the first heavy rainfall after that, there was a new leak and all the old ones were back. We have pretty much ruled out a roof problem and are now wondering whether the plumbing vent pipes might have shifted. One reason is that the new leak appeared in the following manner: during the rainfall I heard dripping noises in an inside wall - the one and only one that goes all the way from the roof to the basement. We subsequently found water almost directly below in the basement, 2 floors down.

The experts have not returned and I am wondering how they would diagnose the problem. A small camera perhaps, or do the walls need to be opened up? Could the same pipe be responsible for the ceiling stains too? (Apparently the old flat roof was not removed when the new one was installed, so it is possible that water flowed in between the two until it found a spot to pool.)

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Plumbing vent (Stack) leak

I am having the exact same problem in exactly same type of house. Would you be able to tell me how you found the cause and how you fixed it? We just had our entire roof replaced in the summer and now we are having these type of leaks. Is the roofer who did the roof responsible for this or do we need to call a plumber? I would appreciate any help on this. Thank you!

Plumbing vent (Stack) leak

more pics to follow....

the first one is the old roof and the next 2 are the new roof...the flashings were replaced as well...the pic was taken before they were replaced.

After the roof was finished we realized the roofer did not put a vent for 2 bathrooms. We had him come back and he had to put a new gooseneck right next to one that is actually useless now! So that involved opening up the roof again. The leaking is happening in this area. We had the roofer come back and he said the roof was fine and that we needed to check the vent pipe.

Plumbing vent (Stack) leak

The next 6 pics are just showing how we had to open up the roof again to have the vents for the bathroom fans. The wall we are hearing the dripping noise inside when it rains is the interior wall. This triplex is attached to another triplex.

Plumbing vent (Stack) leak

The next pics show the water damage coming down to the basement level. We have a main floor and the basement level. Above us, is a tenant that hears the water dripping inside his wall. We hear it in our bathroom wall as well and are starting to see some water damage there. In the tenant's bathroom the ceiling is starting to show some moisture and underneath the wall where they hear dripping is a baseboard heater. There has been moisture and some water underneath there as well.

Before we started hearing dripping in the wall we used to get water leaking into our basement. The tenant changed his shower handle and the ring for the toilet and then it stopped. Then later, when we had lots of rain and wind we got the leak again and hearing the dripping inside the wall. We turned off the main water valve and you could hear the dripping as long as it was raining.

Plumbing vent (Stack) leak

Since the drywall is already screwed up id cut an access hole in the highest point in that area you can reach and start investigating.
If it wasnt leaking before the roof was replaced id still start looking around where the pipes exit/meet roof myself for the leak

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